Fast magnetic relaxation, studied by microwave absorption in neutron-irradiated YBa2Cu3O7?x ceramic

A contactless microwave method is used to measure the fast magnetic relaxation of granular ceramic samples of YBa₂Cu₃O_7−x irradiated by neutrons with fluences of 10¹⁶–10¹⁹ cm⁻². An experimental study of the time dependence of the relaxation of high-frequency (rf) absorption (f=100 MHz) after the action of an external magnetic field pulse has shown the magnetic relaxation times τ ₀ to be in the time interval of 0.5–150 ms. The rf-absorption mechanism is discussed in terms of an intergranular system with a thermally activated flux of vortices and their diffusion in the granular medium. Fiz. Tverd. Tela (St. Petersburg) 39, 977–981 (June 1997)